1. Field of the Invention
The present invention relates to a semiconductor storage device.
2. Background Art
FBC (Floating Body Cell) has recently been developed as a densely integrative memory cell in the place of DRAM. FBC memory devices are composed of transistors formed on SOI substrates. FBC memory devices store data “1” or data “0” by accumulating or releasing holes in or from their floating bodies.
Upon testing a conventional FBC memory device, data was written in a memory cell by a write driver prepared for normal operation, and data was read out from the memory cell by a sense amplifier prepared for normal operation.
Therefore, conventional FBC devices had no means to know the characteristics of memory cells themselves. Especially when their write drivers or sense amplifiers did not work well, it was impossible to evaluate memory cells themselves (T. Ohsawa et al., “Memory Design Using One-Transistor Gain Cell on SOI”, IEEE ISSCC (International Solid-State Circuits Conference), February 2002, Digest of Technical Papers, pp 152–153).
Taking it into consideration, here is provided a semiconductor storage device capable of evaluating the characteristics of its memory cells themselves externally without using a write driver or a sense amplifier.